Betta Fish Care  
Go Back   Betta Fish and Betta Fish Care > Betta Fish Bowls, Habitats, and Accessories
Check out the eBook Betta Fish Care Made Easy
betta fish
Thread Tools Search this Thread
Old 03-18-2012, 08:31 PM   #1 
Aus's Avatar
Join Date: Feb 2012
Location: Australia!
Aquarium Decorations Safe or Toxic?

Bombalurina suggested I make a post about choosing safe rocks to use in an aquarium, as I mentioned in another thread that some minerals are really toxic (I collect minerals as a hobby). While I’m at it, I thought I’d include other decorations as well, such as plastic and ceramic items.

Decorative items sold in pet and aquarium stores that are marked as being specifically for aquarium use are usually very safe. But not all objects you may find around the house or in nature are okay in the fish tank, as some will leach out toxins that will, sooner or later, become toxic to your fish.

So how can you make sure to pick safe items? One way is to use nothing that isn’t from a store and marked specifically for aquarium use. But you can also do a little homework about the likelihood of toxicity in other items, and make good choices based on that.

The following list isn’t 100% comprehensive, but might be useful in helping you choose safe decorations.

Basic common sense: if in doubt, don’t put it in your tank. It’s better to be safe than sorry!


Plastic is one of the most-used materials in fish keeping. Many plastics are completely safe- the acrylic used in fish tanks, for example, and the materials used in plastic plants and other aquarium decorations. Some plastics, however, will degrade in water or release toxins when heated even slightly.

- A general rule to keep in mind is this: if something smells like plastic, don’t use it.

- Soak the item in hot water. If it has a plastic smell after that, don’t use it. If the plastic feels slimy in the water or goes brittle when dried out again, don’t use it.

Really, any plastic decoration that isn’t made for aquariums should be viewed as risky. It might be fine – but then again, it might not.


Most smooth glass items are fine. There’s a couple of exceptions I’m aware of:

- Lead crystal – because… it contains lead.
- Antique glass – because lead was very commonly an ingredient in glass decorations.
- Painted glass – glass paint can be extremely toxic.
- Unsealed mirrors – that stuff on the back of a mirror which makes the glass reflective is often really toxic. Don’t stick mirrors not marked specifically for aquarium use in your tank.


Basically, any item that cannot be used for human food or drink (like raku pottery, which contains a LOT of heavy metals such as copper and lead) should never be used in your fish tank.

Unfired pottery like terra cotta is very porous, so should never be used if there’s a chance it has been exposed to detergents, garden sprays and other toxic chemicals, or used for plants (in case of fertilisers).

Brand new terra cotta can affect ph levels, so it’s best to ‘age’ your pots a while by soaking them in a bucket of tap water before use for at least 24 hours, and then testing the ph.

Avoid ALL metallic glazes. They can be horribly toxic.

Bright red, blue and yellow glazes on non-food grade ornaments that are not specifically made for aquariums MAY be very toxic, and MAY leach poisons into the water. I’d personally not risk it.


The subject of wood in tanks really needs a whole thread to itself, and there’s been a lot of good advice given on this forum already, so I’ll keep it brief:

Wood marked for aquarium use at the LFS is often quite expensive – but this is because it has been aged, pre-soaked, cleaned and treated to make it safe for use. Common woods for sale at LFS’s are Mopani, Bogwood, Redmoor root, Mangrove root and clean driftwood.

Be very careful about using wood you have found outside.

Wood is very porous and absorbs environmental toxins and poison sprays easily, so don’t use wood found in the garden unless you are very sure nobody’s ever used herbicides or pesticides on that land or nearby as sprays can drift a long way.

Some wood contains sap that can be extremely toxic in general, especially when the wood is green. To be safe, never add any unidentified wood to your tank.

Never use green wood (cut less than a year, or better, two years ago) in your tank – some wood that is safe when completely dry is not safe when green, or even for several years after it’s been cut. It may contain sugars and starches that will upset your tank’s chemistry, or toxic sap.

Shells and Coral

These aren’t recommended for use in freshwater tanks, because they contain calcium which dissolves in water and can dramatically increase the ph and hardness levels.


Not every rock is safe for aquarium use, especially in water with low ph.

Aside from the danger of sharp or jagged edges and rough surfaces, some rocks contain high levels of toxic minerals and elements (like lead and arsenic) that can leach out into the water and will quickly poison your fish.

Low ph makes water soft and acidic, which frees otherwise inert (safely 'locked up') minerals and elements from the rock so they leach into the water, making it toxic.

Some minerals (like fluorite and calcite) will dissolve in water and affect your water chemistry.

Speaking VERY generally, the safest rocks:

- Are extremely hard and will not go soft even after a month of being soaked in water, and do not shed a lot of particles or scratch badly when scrubbed with a scourer.
- Do NOT have any metallic particles in them, something you sometimes can’t tell without a microscope…

Generally regarded as safe:

- Basalt
- Clear and white quartz (don’t use spiky crystal clusters, for obvious reasons, and avoid any quartz that contains glittery fool’s gold, which can be very toxic).
- Igneous rocks (Obsidian, Granite & Gneiss – watch out for sharp bits, though)
- Petrified wood
- Very hard, smooth, water-worn ‘river rocks’ (must be boiled before use, don’t oven-heat though as some will explode in dry heat).

Cautionary, best avoided:

- Shale and slate can contain pyrites (poisonous metals) and sometimes fossil oil residue. I’d avoid collecting them for aquarium use, just in case.

- Limestone, dolomite, marble, sandstone, siltstone, calcite, fluorite and other ‘soft’ and ‘brittle’ rocks contain minerals that will dissolve in freshwater tanks and quite seriously mess up your water chemistry.

- Brightly coloured minerals and crystals you might find at a new age store, gift store or market - like Turquoise, Malachite and Azurite, which have very high levels of copper and/or aluminium, and Lapis lazuli which very often contains toxic pyrites.

AVOID at all costs:

- Any ore (metal bearing rock), and any metallic or ‘glittery’ minerals - these will almost certainly poison your fish.

Last edited by Aus; 03-18-2012 at 08:43 PM.
Aus is offline   Reply With Quote
Old 03-18-2012, 08:39 PM   #2 
wystearya's Avatar
Join Date: Sep 2010
Location: WV
Lead Crystal leaks lead..? Then how can they sell them as drinking glasses, like for wine..?

I'm just curious! >> I think this is a great topic, and I am glad to have the information. <3
wystearya is offline   Reply With Quote
Old 03-18-2012, 08:52 PM   #3 
Aus's Avatar
Join Date: Feb 2012
Location: Australia!
Lead crystal -can- be dangerous if acidic stuff ( wine..) is stored in it for long periods, as stated in this article:

It's also recommended that pregnant women and children avoid lead glassware, so I'm pretty sure it shouldn't go in the fish tank, just in case.

From another article:

"Preliminary tests have shown that, over time, significant amounts of lead can migrate from lead crystal containers into liquids stored in them.
  • One research team measured the amount of lead migration in Port wine that was stored in lead crystal decanters. After two days, lead levels were 89 micrograms; after four months, lead levels were between 2,000 and 5,000 micrograms.
  • White wine doubled its lead content within an hour of storage, and tripled it within four hours.
  • Brandy stored in lead crystal for five years had lead levels around 20,000 micrograms.
  • Any liquid can leach lead from crystal just as effectively as wine and other alcoholic beverages.
To put these numbers into perspective, the EPA’s lead standard for drinking water is 50 micrograms per liter."

Last edited by Aus; 03-18-2012 at 08:54 PM.
Aus is offline   Reply With Quote
Old 03-18-2012, 08:54 PM   #4 
wystearya's Avatar
Join Date: Sep 2010
Location: WV
Learn something new every day!

Thanks for the link. :)
wystearya is offline   Reply With Quote
Old 03-19-2012, 01:17 PM   #5 
Join Date: Jul 2010
Location: Philadelphia
Thank for information it good to know.

Just want to say something about plants. I was using plants at the beginning about 4.5 years ago when i just got my very first betta. I used to buy them in the pet store. Then i stopped because i saw that they kept them in the tank with fish. So i was afraid that they carry disease.
Now i found out that you need to quarantine the plants for 2-3 weeks before you use them , because they are carry disease.

I don't buy any plants from pet store. I am using spider plant which very easy to take care of and they stay longer than other plants. My mom has them and my friend has them. I think a lot of people familiar with spider plants. They can vary in color, size, shape of the lives. My bettas love them. I wish everyone know that and don't spend money on pet store plants which can carry disease and kill your fish.

Rocks i always buy just natural rocks in the pet store. I try to avoid colored rocks. Also i bought a few times river rocks. Black and white rocks i never had problems. But river rocks a little bit expansive. Tell you the truth i brought rocks from the shore. When i am going on vocation i always bring rocks. But i soak them in the water before i am using them.
ANHEL123 is offline   Reply With Quote
Old 03-19-2012, 02:41 PM   #6 
Join Date: Mar 2010
Location: USA
Awesome job......great information.....

Please, please be careful boiling or baking rocks.....while the odds of an explosion is can happen and why take the chance when you have other safer methods....if you do opt to boil the it outside away from your house.....better safe than sorry......
Oldfishlady is offline   Reply With Quote
Old 03-19-2012, 04:01 PM   #7 
Join Date: Jul 2010
Location: Philadelphia
So any disease that fish had we can sterilize the gravel and use it for another fish?

I agree why take a chance if we can boil them. For how long we should boil them?
ANHEL123 is offline   Reply With Quote
Old 03-19-2012, 05:05 PM   #8 
DoberMom's Avatar
Join Date: Feb 2012
Location: Orange County, Cali
Wait, so no ceramic figurines that I can find online should go in my tank?? :( is there no way to make them safe?
DoberMom is offline   Reply With Quote
Old 03-19-2012, 05:09 PM   #9 
Wolfie305's Avatar
Join Date: Jan 2012
Location: Wareham, MA
Is something like a flower pot okay to put in freshwater tanks?
Wolfie305 is offline   Reply With Quote
Old 03-25-2012, 08:52 PM   #10 
Aus's Avatar
Join Date: Feb 2012
Location: Australia!
Originally Posted by DoberMom View Post
Wait, so no ceramic figurines that I can find online should go in my tank?? :( is there no way to make them safe?
I'm not an expert on that, but I do know some glazes will dissolve and release harmful stuff into water, like raku pots which contain arsenic and lead in the glaze.

From the research I've done, pretty much any food-grade ceramics are safe, as nobody wants lead or other poisons in their food, and they are generally fired hard so the clay won't dissolve, etc.

Not sure about ornaments, I have no information on what might be safe and what might not as far as they go. I do know a lot of antique glazes used some pretty hardcore poisonous minerals for colouring, etc.

I think some more research into this is warranted. I'll see what I can do there, or maybe there's somebody here with a degree in pottery or something who could offer advice on possible toxins.
Aus is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Fish Safe Decorations? Lauren85 Betta Fish Bowls, Habitats, and Accessories 7 10-21-2010 08:09 PM

All times are GMT -5. The time now is 09:43 PM.

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.